In order to start the internal combustion engine of small vehicles, such as a snowmobile, a recoil starter is sometimes provided. To start the engine, the user pulls on a rope of the recoil starter which causes the crankshaft of the engine to turn. If the crankshaft turns fast enough, the engine can be started. If not, the rope needs to be pulled again until the engine starts.
In order to facilitate the starting of the engine, some vehicles have been provided with an electric starting system. This system consists of an electric motor, known as a starter motor, which engages and turns a ring gear connected to the crankshaft when an ignition key is turned or a start button is pushed by the user. The starter motor turns the crankshaft fast enough to permit the starting of the engine, and once the engine has started, disengages the ring gear and is turned off.
Although it is very convenient for the user, electric starting systems of the type described above have some drawbacks. The starter motor and its associated components add weight to the vehicle. As would be understood, additional weight reduces the fuel efficiency of the vehicle, affects handling of the vehicle and, in the case of snowmobiles, makes it more difficult for the snowmobile to ride on top of snow. These electric starting systems also require additional assembly steps when manufacturing the snowmobile and take up room inside the vehicle.
The vehicle has a battery to supply electric current to the starter motor in order to turn the crankshaft. To recharge the battery and to provide the electric current necessary to operate the various components of the vehicle once the engine has started, an electrical generator is operatively connected to the crankshaft of the engine. As the crankshaft turns the rotor of the electrical generator, the generator generates electricity.
In recent years, some vehicles have been provided with starter-generator units which replace the starter motor and the electrical generator. The starter-generator is operatively connected to the crankshaft in a manner similar to the aforementioned electrical generator. The starter-generator unit can be used in a starter mode or a generator mode. In the starter mode, by applying current to the starter-generator unit, the starter-generator unit turns the crankshaft to enable starting of the engine. In the generator mode, the rotation of the crankshaft as the engine operates causes the starter-generator to generate electricity. As would be understood, the use of such systems addresses some of the deficiencies of starting systems using separate starter motors and electrical generators.
In order to start the engine, the torque applied to the crankshaft to make it turn has to be sufficiently large to overcome the compression inside the engine's cylinders resulting from the pistons moving up in their respective cylinders as the crankshaft rotates. In order to provide this amount of torque, the starter-generator unit needs to be bigger to properly operate in the starter mode than it would have to be if it was to be used only as an electrical generator. As such, the starter-generator is also heavier than it would have to be if it was to be used only as an electrical generator.
There is therefore a need for a method and system for starting and internal combustion engine that address at least some of the above inconveniences.